Fuse for antiaircraft shells



Patented Feb. 18, 1947 UNITED STATES PATENT OFFICE FUSE FOR ANTIAIRCRAFT SHELLS Philip W. Allison, Galveston, Tex.

Application May 10, 1943, Serial No. 486,400

(Granted under the act of March 3,1883, as amended April 30, 1928; 3.70 O. G. 757) 14 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to the time fuse mechanism for shells andother explosive missiles which are .designed to explode after a predetermined, and usuallyadjustableinterval of time after having been fired from a gun, thrown by hand or dropped from aircraft. For convenience the improved ,fuse will be described in connection with antiaircraft shells, although his clear that the invention is not limited to this use.

The object of the invention is to devise a fuse which will obviate the necessity for clockwork now used in such cases and which by reason of its necessarily delicate mechanism is too easily subjecttoderangement by the shock accompany- .ing the projecting of the shell and its flight.

Allied with the object, other purposes include'the devising of a fuse which will be reliable and 001- proof inoperation, and not costly :tomanufacture in quanties.

For the attainment of these and such'other obiects of invention as may herein appear or be pointed out I have shown an embodiment of my invention in the accompanying drawing, wherein Fig. 1 is a sectional view of the improved .fuse in elevation;

,Fig. 2 is an elevational view thereof;

Fig. 3 is a sectional ,plan view taken as the line 3-3 of'Fig. 1,;

,Fig. i'is likewise a sectional plan view but taken nearer the tip of the fuse, on line 4-4 of Fig. 1,;

Fig. :5 is a detail of therotor;

Fig. ,6 is a detail-of the .speed-of-rotation 'gov- .ernor, and

Fig. 7 is a detail of the square external thread whichis-integral with, .and uprising from, the

fuse base.

portion and the lower portion being .in the rear.

The invention utilizes the rotation of the shell and the air-pressure .on the nose to produce a constant difierential speed of rotation between the shell itself and a rotor contained in the .nose, and thereby operate a gear-train which will re- .lease a striker after a predetermined lapse of time. It has been found-by experiment that, .al-

though the linear velocity of a shell decreases rapidly, due to air resistance and the gravity component, the rotational velocity remains practically constant throughout its flight. This principle of constant rotational velocity is utilized in the mechanical time-fuse now used in our armed services, where the centrifugal force of weights in the fuse is used to operate a clockwork mechanism. The :fuse proposed herein will obviate the necessity for clockwork, with its necessarily delicate mechanism, subject to derangement by shock.

In the proposedmechanism, arotor is mounted longitudinally in the fuse, on anti-friction bearings. Upon firing, the set-back seats this rotor firmly upon the fuse body, thereby permitting the rotor to acquire the same rotational velocity as the shell itself. When acceleration ceases, the rotor is freed. Air entering through holes v-inthe fuse casing and impinging on inclined vanes in the rotor ,head causes an increased rate of rotation of the rotor. When this difierenial rate of rotation reaches a certain value, a centrifugal governor on the rotor (similar to the touch-andgo governor on a phonograph) holds the rotor rotation to that speed, regard-less of variationof air pressure. This constant differential rate ;of rotation betweenrotor and fuse body causes constant speed operation of a double-reduction set of worm gearing, which, after a predetermined time-interval (dependent .upon initial setting) causes the tripping of a spring-operated striker in the rotor itself, the striker impinging upon .a detonator and causing explosion of the shell.

The fuse casing I0 is rotative'ly mounted on the fuse base ll, as by means of a ring 9 which is fitted over an inwardly-turned flange 29 of the fuse casing and which is secured 'to the fuse base I I as by screws shown. The fuse base itself is secured to the shell casing l by screwing a threaded nipple l2 depending from the fuse base H, into the tapped mouth of the shell casing. The shell casingcontains the usual 'high explosive filler 2, booster charge 3, and detonator 4. Detonator 4 is set off by primer point or striker 24 which is the lowermost element of a primer assemblage, the other elements of which are a .follower member 22 and a compression spring 23 desposed between the striker 24 and the follower 22. The primer assemblage is contained within a tubular rotor 30, the follower being mounted within the said tubular rotor for .an extent of sliding movement. Follower 22 is made in the form of a. one-way*ba11.clutch, and comprises a number of balls 25. Striker spring 23 is normally under only slight compression, in the position of the parts shown in Fig. 1. When the shell is fired from the gun, upwardly in Fig. 1, set-back causes follower 22 to move to the rear downwardly in Fig. 1, fully compressing the striker spring. Ball clutch 25 then becomes effective to hold the follower in the rearward position.

during flight of the shell, thereby keeping the striker spring fully compressed. The striker 25 is prevented from being moved rearwardly, downwardly, Fig. 1, under urgency of the said compressed striker spring by three steel balls 2|, only two appearing in Fig, 1, which are contained in suitable pockets provided for them in the striker as clearly seen in Fig. 1. As seen in Fig. 1, portions of the balls 2| extend beyond the strikerand are received in passageways 3| provided for them near the lower end of tubular'rotor 30, see also the detail of the rotor in Fig. 5. Although passageways 3| are sufliciently large to permit the balls to pass through, the balls are held in place by a retainer ring 4| which in the normal turning. As soon as the shell has left the gun,

acceleration ceases; spring washer 20 resumes its normal. shape lifting the rotor overhang from its position of the parts during flight, as shown in Fig. 1, blocks escape of balls 2|, which are thus effective to prevent downward movement of striker 24.

Retainer ring 4| is elevated, at the instant the fuse is set to explode the shell, by the rotor and the following parts associated therewith. The upper end of retainer ring 4| is provided with a flange 40 which rests on a ring gear 50, or rather, on ball-bearings between the two, as clearly seen in Fig. 1. -The ring gear is pro- Vided at its upper end with external threads 52 which receive a threaded cap 53 in a manner to hold flange40 of the retainer ring between the cap 53 and the ring gear 50. The retainer ring 4| is thus caused to move with the elevational movement of the ring gear 50. The ring gear is mounted for a limited extent of vertical movement by the provision of an internal square thread 55 which makes a single or a partial convolution and which is received in the interdental space between a square thread l5 formed externally on a hub l4 uprising from the fuse base The teeth of the wide-face ring gear 50 mesh with a pinion secured at the lower end of a short vertical spindle 6| which is rotatively mounted in a bracket |3 secured on fuse casing Ill; The bracket also mounts-a doublereduction worm gear train 62 the last unit of whichmeshes with a worm 32 secured on the rotor 30.

Tli'e'forward end, upward in the figures, of the rotor 30 is implemented with inclined vanes '36 upon which air'impinges by passing through time of firing, For this purpose the forward end of the 'rotor is provided with an overhanging portion 38 which overlies an annular flange l8 secured within the fuse casing H1. Annular flange I8 is provided with a plurality of holes IQ for passage of the air entering fuse casing ports lb and leaving the rotor vanes 36. In the" normal position of the parts, as shown in Fig. 1, the

rotor overhang 38 is raised so as to clear contact with the fuse flange l8. It should be mentioned that the rotor 30 is capable of a limited extent of vertical movement made possible by the sliding engagement of the lower rotor bearing 35. Un-

derlying rotor bearing 35 and desposed between seat'on annular flange l8 and permitting the rotor to turn-m The rotor is provided with a centrifugal governor to maintain its rotation at a constant predetermined rate. The governor comprises a plurality of bell-crank levers 33 pivotly mounted at 33a to a collar 34 secured to the rotor and provided with weights 33w at the lower ends of the vertical legs of bell-cranks 33. The weights may be connected by springs, as shown in Fig. 6. The horizontal legs of the bell-cranks underlie the horizontal annular disc portion of an L-shaped flanged collar 31 which is slidably mounted on the rotor for a limited extent of vertical movement. A compression coil spring 31s is disposed between the upper end of slide collar 31 and a seat in the rotor overhang 38, urging the collar 31 downwardly against the upwardly directed force of the weighted bell-cranks 33. On the horizontal annular'disc portion of slide collar 31 are a number of upstanding plungers 317) which clear through holes provided for that purpose in annular flange I8.

Centrifugal force' caused by rotation of the rotor (at a higher speed than that of the entire shell) causes governor weights 33w to swing outwardly against the tension of the governor springs (Fig. 6) and pressing the horizontal legs of bell-cranks 33 against the horizontal flange portion of the slide collar 37 to raise the collar upwardly against the force of spring 31s. This upward movement of the collar forces its plungers 31p against the rotor overhang 38, thereby slowing it down until the governor weights move inas a result of reduced speed of rotation-to relieve the pressure on the governor plungers.

The improved fuse of this invention operates as follows: Before firing, the nose 'of-' the shell, the fuse casing (I0) end, is placed in a fusesetter and, while the shell casing I is held stationary, is rotated the required amount relative to casing l. Rotation of fuse casing I0 carries the worm gear train-with it (as the latter is mounted thereon)." Since a worm gear is irreversible, the gear train is turned orbitally in frozen condition with the fuse casing. (The rotor too is turned together with the fuse casing and the worm'gear train.) Pinion 60, turning as part of the gear train, being in mesh with the ring gear 50, will rotate gear 50 relative to the fuse base H, i. e., relative to shell casing The rotation imparted to ring gear 50 will cause an elevationof the ring gear as its internal square thread 55 rides up on the external square thread I5 of the fuse base Elevation of rin'ggear 50 carries withit the retainer ring 4|, by-reason of the connection between the two described above. But the retainer ring 4|, in the setting of the fuse, is never raised sufliciently to permit passage of the stop ball 2|, so that the striker 2E is maintained by the balls 2| against downward movement. I p I 3 The round, after the setting of-its fuse as de- "scribed', is then loadedintoth *gimand flr'ed.

his already described, the firing causes a loading or compressing of striker coil spring 23; and, also described above, set-back causes the rotor to be held against turning. As soon as acceleration sufficiently decreases, the rotor becomes free tobe rotated'by the air coming in at nose ports 16, as already described. The rotor acquires a speed of rotation which is higher than that of the shellitself and which, because of the functioning "oi the centrifugal governor, is constant. The gear train, including the worm reductions;

is thus rotated at a constant speed to cause aslow but constant rotation of ring gear 58 and a slow elevation (or forward movement) of the gear and the retainer ring M. The latter is not fig-idly secured to the rotor but i permitted to be turned by the ring gear by reason of the reaction through the ball bearings 'between the ring gear 50 and flange Mi under the pressure imposed b the compressed striker spring 23. 7 When the ring gear is sufiiciently turned and the retainer ring 44 sufiicientl-y raised, the retainer balls 2| are free to escape through the passages -3l of the rotor; whereat the striker 24 impelled by its spring 123 impinges downwardly to strike the detonator 4.

It will be noted that a predetermined amount of rotation of ring gear 55 is necessary before the striker 124 is released to its spr e- This ro t on is secured in two ways (a) by initial setting of the fuse setter and (b) by operation of geartrain. Hence, the greater amount of rotation in initial setting, the less will be required by geartrain. Accordingly, this fuse setting is opposite to conventional varieties, in that a shorter rotation of fuse setting causes a longer time of flight before fuse operates.

I claim:

1. In a time fuse for shells having a shell casing, a nose casing rotatively mounted thereon, and a detonator, the combination of a tubular rotor rotatively mounted in the said nose casing, a striker slidably mounted within the said tubular rotor and having a primer point contactable with the said detonator, spring means urging the striker towards the detonator, the said striker having a plurality of cupped cavities and the said tubular rotor having a plurality of holes aligned with the said cavitie of the striker, a plurality of balls contained in the said cavities and the said holes, a retainer tube encircling the tubular rotor and covering its said holes whereby the balls are imprisoned in their said cavities to block the striker from moving towards the detonator under urgency of its said spring, a worm secured on the rotor, a double-reduction worm gear train mounted on the said nose casing with its high speed worm gear meshing with the said rotor worm and provided with a pinion on its low speed spindle, a ring gearmounted about the said rotor and provided with an internal screw thread, the said fuse casing being provided with an uprising annular hub having an external screw thread on which the said ring gear is screwed, the said ring gear having spur gear teeth meshing with the said pinion whereby rotation imparted thereby to the ring gear will cause 1ongitudinal movement thereof, the ring gear being operatively connected to the said retainer tube whereby the said longitudinal movement of the ring gear will move the said retainer tube to uncover the said holes of the tubular rotor whereby the said balls may escape therethrough under urgency of the said striker spring and centrifugal force of the rotation of the said parts, thereby releasing the striker to its said spring.

2; In a time fuse for shells having a shell easing, a nose casing rotatively mounted thereon, and a detonator, the combination o'f a. tubular rotor rotatively mounted in the said nose casing, a striker slidably mounted within the said tu-' bular rotor and having a primer point -contact able with the said detonator, spring means urging the striker towards the said-detonator, the said strikerhaving a plurality of cupped cavities and the said tubular rotor having a plurality of holes aligned with the said cavities of the striker, a plurality of balls contained in the said cavities and the said holes, a retainer tube encircling the tubular rotor and covering its said holes whereby the balls are imprisoned in their said cavities to block the striker from moving towards the detonator under urgency of its said spring, a gear mounted about the said rotor and provided with an internal screw thread, the said fuse casing being provided with an uprising annular hub having an external screw thread on which the said ring gear is screwed, speed reduction means between the rotor and the gear whereby rotation imparted to the gear will-cause its longitudinal movement, the gear being oper atively connected to the said retainer tube whereby the said longitudinal movement of the 'ring gear will move the said retainer tube to uncover the said holes of the tubular rotor whereby the said balls may escape therethrough under urgency of the said striker spring and the centrifugal force of the rotation of the said parts, thereby releasing the striker to its said spring.

3. In a time fuse for shells having a shell casing, a nose casing rotatively mounted thereon, and a detonator, the combination of a tubular rotor rotatively mounted in the said nose casing, astriker slidably mounted within the said tubular rotor and having a point contactable with the said detonator, spring means urging the striker towards the said detonator, the said striker having a plurality of cupped cavities and the said tubular rotor having a plurality of holes aligned with the said cavities of the striker, a pluralityof balls contained in the said cavities and the said holes, a retainer tube encirclin the tubular rotor covering its said holes whereby the balls are imprisoned in their said cavities to block the striker from moving towards the detonator under urgency of its said spring, a member mounted for combined rotary and longitudinal movement and operatively connected to the said retainer tube, and speed reduction means between the rotor and the said member whereby rotation imparted by the rotor to the said member will move the said retainer tube to uncover the said holes of the tubular rotor whereby the said balls may escape therethrough under urgency of the said striker spring and the centrifugal force of the rotation of the said parts, thereby releasing the striker to its said spring.

4. The combination according to claim 3- in which the rotor is provided at its tip end with vanes and the nose casing is provided at its tip with air entry ports and the shell casing is provided with air egress ports.

5. The combination according to claim 3 in which the rotor is mounted for a limited extent of longitudinal movement and is provided with an externally-disposed annular flange, the said nose casing being provided with an internallydirected annular flange, and spring means for urging the rotor in a forward direction to maintain its said flange removed from the said flange of the nose casing, the said rotor being moved by set-back upon firing to contact its flange on the nose casing flange whereby the rotor is held against turning.

6. The combination according to claim 3 in which the nose casing is provided with an internal annular flange and the rotor is provided with a plurality of bell-crank levers the vertical legs of which are parallel to the axis of the rotor and weighted, the horizontal legs being contactable with the said annular flange as the weighted legs of the bell-crank swing outwardly due to centrifugal force when the rotor turning exceeds a. predetermined amount.

7. The combination according to claim 3 further provided with a follower member slidably mounted in the said tubular rotor, the said follower member being implemented with a oneway ball clutch cooperative with the wall of the tubular rotor and a compression spring disposed between the said striker and the said follower member.

8. In a time fuse for shells having a shell casing, in combination, a shell having openings leading from its forward end through its walls to the atmosphere, a hollow nose on the shell and rotatable relative thereto, said nose having air passages adjacent its front end communicating with openings in the shell through the nose, a rotor rotatably mounted in said nose an provided with propeller means adjacent said passages against which air impinges during the flight of the shell to rotate the rotor, a spring-backed striker carried bythe rotor, means for latching the striker to the rotor, a member axially movable relative to the rotor, and operable connections between said rotor and axially movable member to move said member when the rotor is rotated to render said latching means ineffective and release the striker, and a detonator positioned to be engaged by the striker.

9. In a time fuse for shells having a shell casing, in combination, a hollow nose carried by said shell and rotatable relative thereto, said casing having air passages adjacent to its front end, means rearward of said passage for the escape of air entering said passages, a tubular rotor rotatably mounted in the nose and positioned axially thereof and provided with propeller means adjacent the nose passages for impingement of air to rotate the rotor during the flight of the shell, a striker slidably mounted in the rotor, a spring backing the striker, means for normally latching the striker against movement, a gear surrounding the rotor and axially movable relative thereto and threadedly connected to the shell, a worm carried by the rotor, a worm gear train connecting the worm on the rotor with the rotor surrounding gear whereby when the rotor is rotated the surrounding gear will be axially moved relative to the rotor according to the setting of the nose on the shell, and means operable by the gear to unlatch the striker upon the axial movement of said gear, and a detonator positioned to be engaged by the striker.

10. The invention of claim 9 characterized in that the rotor is provided in its forward end with means operable upon set-back to compress the striker spring and hold the same compressed.

11. The invention of claim 9 characterized in that the means for compressing the spring in the rotor comprises a one-way ball clutch moved rearwardly by set-back.

12. The invention of claim 9 characterized in that there is spring means interposed between the rear end of the rotor and the shell body compressed by the rotor upon set-back to seat the rotor and prevent it from turning during firing, but adapted to restore the rotor to normal rotatable position upon cessation of acceleration of the shell.

13. The invention of claim 9 characterized in that the rotor is provided with a collar to which is attached a plurality of centrifugal governor arms, and means carried by the nose cooperating with said arms to assure the rotation of the rotor and shell at substantially the same speed.

14. In a time fuse for a shell having a casing, in combination, a shell having openings leading from its forward end through its walls to the atmosphere, a hollow nose on the casing and rotatable relative thereto, said nose having openings in its forward end communicating with openings in the shell through said nose, a hollow rotor axially mounted in the nose and having propeller means within the nose adjacent nose openings, whereby the rotor is rotated in the flight of the shell, a striker slidably mounted in the rotor, a spring in said rotor backing the striker, a follower in the rotor operable upon set-back to tension said spring and hold it tensioned, said rotor having oppositely disposed apertures in its wall, oppositely disposed pockets in the striker, locking devices partly in the apertures of rotor and partly in said pockets, a member rotatably carried by the shell and rotatably surrounding the rotor and movable axially thereof, means interposed between the rotor and said member for moving said member upon rotation of the rotor, and a retainer ring surrounding the rotor and normally holding said locking devices in said pockets and apertures, said retainer rin moved by the rotor surrounding member to release the locking devices and surrender the striker to its spring.

PHILIP W. ALLISON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,817,503 Anderson Aug. 4, 1931 565,172 Maubeuge Aug. 4, 1896 1,320,991 Saal Nov. 4, 1919 1,681,390 Bold Aug. 21, 1928 1,549,763 Greenwell Aug. 18, 1925 1,309,771 Newell July 15, 1919 1,000,862 Voller Aug. 15, 1911 1,486,593 Lucas Mar. 11, 1924 1,596,224 Wiley Aug. 17, 1926 880,818 Pangher Mar. 3, 1908 FOREIGN PATENTS Number Country Date 473,282 British Oct. 6, 1937 749,464 French May 8, 1933 10,607 British May 5, 1904 

